Brooklyn CrimProf Jason Mazzone wrote "Homeland Security and the Lost Protection Clause." The abstract states in part:

In our federal system of government, who is responsible for securing the homeland? Although Congress has made available to states and cities some funding for overtime and equipment, it has not taken responsibility for covering all of the security costs incurred locally. While deploying some federal personnel for domestic security, the Executive branch relies largely on state and local officials for the necessary manpower. . . . Ratified in an age of insecurity, the Constitution of the United States provides clear guidance on the issue of responsibility for homeland security. The key is the largely forgotten - or lost - Protection Clause of Article IV. The Protection Clause requires the national government to safeguard states and their cities from attack, either by deploying federal personnel to provide the necessary security or paying the costs of security measures implemented locally. . . . In fulfilling its security obligations under the Protection Clause, the national government may enlist the assistance of state and local personnel so long as it pays the costs of doing so.